Digital camera which detects a connection to an external device

ABSTRACT

An electronic camera and method of operating an electronic camera which detects whether an external device such as a personal computer is properly connected to the camera and in a state which permits communication. The camera monitors a data terminal ready (DTR) signal of an RS-232 connection in order to determine that the external device is properly connected and in a state which permits communication. Once the proper connection is detected, the camera can either transmit or receive images and/or audio from the external device. Accordingly, a specific switch which places the camera in a communication mode can be eliminated. Further, a single switch may be utilized for both controlling whether the camera records or plays images when there is no device connected, and which controls whether the camera transmits or receives images and/or audio when an external device is determined to be connected.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is related to commonly owned co-pending U.S. patentapplication Ser. No. 08/535,378 entitled “Digital Electronic CameraHaving an External Input/Output Interface Through Which the Camera isMonitored and Controlled” and U.S. patent application Ser. No.08/535,562 entitled “A Digital Electronic Still Camera Which Receives anInput/Output Control Program Through a Detachable CommunicationInterface Card”, both of which were filed on Sep. 28, 1995 and areincorporated herein by reference. This application is also related tocommonly owned co-pending U.S. patent applications Ser. No. ______entitled “Method and System for Reading and Assembling Audio and ImageInformation for Transfer Out of a Digital Camera”, and Ser. No. ______entitled “External Communication Interface for a Digital Camera”, eachconcurrently filed with the present application and incorporated hereinby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a digital electronic camera and theinterfacing of the camera to an external processing device whichmonitors, receives images and/or audio, and/or controls the camerathrough an input/output interface. The invention is more particularlyrelated to a digital electronic camera which automatically detects aconnection to the external processing device.

2. Discussion of the Background

Conventional cameras which use light sensitive film have been known fora long time and the manner of generating images is well-known; lightsensitive photographic film is exposed to light which passes through alens and a shutter. The film is then taken to a developing center andprocessed into photographic prints.

Digital electronic cameras which electronically capture images or imagesalong with audio are also known. However, this field of technology isrelatively new and there is not a universal standard for exporting orproducing images from digital cameras. When designing the cameracorresponding to the present invention, the inventors have discoveredvarious problems in communicating information out of the camera. Theseproblems include the connection of the camera to an external device suchas another camera or a general purpose computer. The present inventorshave sought to overcome problems pertaining to the actual connection ofthe camera to the external device, the conversion of signal levels froma level used by the processor within the camera to a level compatiblewith a communication interface, the detection of a connection of thecamera to the external device, and the manner of assembling theinformation to be transmitted.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide anelectronic camera capable of detecting that there is a proper connectionand communication with an external device such as a computer. It is afurther object of the invention for the camera to transmit and receiveimages and/or audio from the external device after the connection hasbeen established. It is yet another object of the invention to providean electronic camera which operates without utilizing anelectrical-mechanical switch for placing the camera in a communicationmode. It is yet another object of the invention to provide an electroniccamera which operates using a single switch to control both whether thecamera plays images and records images when the external device is notdetected to be connected, and which also controls whether the cameratransmits or receives images when the external device is determined tobe properly connected to the camera.

These and other objects are accomplished by an electronic camera forconnection to an external device such as a personal computer. Theelectronic camera periodically checks, for example, every one-half toone second, whether the camera is connected to the external device andalso whether the external device is in a state which permitscommunication. After it is determined that there is a proper connectionand the external device is in a state which permits communication, thereis a communication between the electronic camera and the external deviceof images and/or audio.

Preferably, the camera detects proper connection to the external deviceand that the external device is in a state which permits communicationby monitoring a data terminal ready (DTR) signal of an RS-232connection. This DTR signal will indicate both that the external deviceis properly connected and ready to communicate.

In an embodiment of the invention, the camera includes a single switchfor both controlling whether the camera captures images through the lensor plays images back to the user on a video screen, and whether thecamera is to transmit or receive images and/or audio or transmit theimages and/or audio when the external device is detected to be connectedand capable of communicating. By detecting that the external device iscapable of communicating, it is possible to eliminate a separate switchwhich places the camera in a communication mode.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1A illustrates a perspective view of the front and top of a digitalcamera according to the present invention;

FIG. 1B illustrates another perspective view of the digital camera ofFIG. 1A viewed from the bottom and rear;

FIGS. 2A-2C illustrate perspective views of an external communicationinterface of the camera;

FIG. 3A illustrates a top view of a latching mechanism of the externalcommunication interface;

FIG. 3B illustrates a cross-sectional view of the latching mechanism ofthe external communication interface;

FIG. 4A illustrates a view from the top of a pivoting latch member ofthe latching mechanism;

FIG. 4B illustrates a cross-sectional view of the pivoting latch member;

FIG. 5A illustrates the manner of inserting a latch 196 of the pivotinglatch member into a receiving member;

FIG. 5B illustrates the latch 196 after being inserted through andlatched to the receiving member;

FIG. 6A illustrates a top view of the latch locked into the receivingmember;

FIG. 6B illustrates the pivoting latch member in a release position inwhich the pivoting latch member has rotated about pivot point 214;

FIG. 7 is an exploded view of the internal components of the externalcommunication interface;

FIG. 8 is a functional block diagram of the electrical aspects of thedigital camera;

FIG. 9 illustrates the details of the CPU 23 of the camera;

FIG. 10, illustrates a functional block diagram of the memory card 16employing four flash memories;

FIG. 11 is a flowchart illustrating the process of capturing an imageand audio by the camera;

FIG. 12 illustrates the manner of storing files within the memory card16 and the format of information to be transmitted out of the camera;

FIG. 13A illustrates a single switch which controls both whether thecamera is recording, playing or is off along with whether the camera isreceiving or transmitting when connected to an external device;

FIG. 13B illustrates two switches; one for placing the camera in areceive or a transmit mode and the other for setting the camera to arecord mode, play mode or turning the camera off;

FIG. 14 illustrates a flowchart of the communication process of thecamera with an external device;

FIG. 15 illustrates the manner of transmitting information of the camerato an external device;

FIG. 16 is a flowchart illustrating the specific steps for receiving andstoring by the camera data from an external device;

FIG. 17 is a functional block diagram of the electrical componentswithin the external communication interface; and

FIG. 18 illustrates a timing diagram showing how power to thecommunication circuitry is reduced in order to conserve the life of acamera battery.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings wherein like reference numerals designateidentical or corresponding parts throughout the several views, and moreparticularly to FIG. 1A thereof, a perspective view showing the frontand top of a digital electronic camera according to the presentinvention is illustrated. The camera, referred to as a digital camera orelectronic camera, captures images and/or audio and writes thisinformation into a memory in digital form. The use of photographic filmis not necessary and the camera may capture a series of consecutivestill images to provide video with movement or motion. The camera 100illustrated in FIG. 1A contains a button 102 for turning the flash 20 onand off and changing the flash mode, a button 104 for setting therecording mode such as whether audio is to be captured, whether a seriesof consecutive images are to be captured, etc. A display 22 is a LCDdisplay which displays the state and settings of the camera such as theflash mode, record mode, battery state, number of images taken and otherfeatures of the camera. Switch 108 is used to set the self timer andswitch 110 is used to turn the camera off and on and also sets whetherthe record mode or play mode is to be used. This switch in oneembodiment is also used to set whether the camera will be in a transmitor receive mode when connected to an external device. There is a red LED112 which indicates that an image is being recorded or that the selftimer is operating. The windows designated by 114 are used to performautomatic focusing and the viewfinder window is designated by 116.Images are captured through the lens 7, and there is a window 118 forreceiving commands from an infrared remote control (not illustrated)which can be used to instruct the camera to capture images and/or audioand also control the functions of the camera. There is also a clip 120which holds a camera strap. A slidable lever 122 is used to zoom thelens and the camera also includes a shutter release button 124.

FIG. 1B illustrates a perspective view of the bottom and back of thecamera 100. There is knob 130 to adjust the visibility, a cover 132which covers an opening for a small button type battery used to maintainthe setting of parameters in memory, a view finder 134, a date button136 and time button 138 which controls the operation of the date andtime functions of the camera, a microphone 140, and a switch 142 forcontrolling the image quality or resolution. There is a hole 146 forreceiving a bolt from a tripod, and a lever 148 for releasing memory orI/O cards from the camera body through the slot 160.

The camera according to the present invention allows images and audio ina digital format to be transmitted from and received by the camera toand from an external communication interface which connects to aconnecting portion 150 of the camera. The connecting portion 150includes concave protrusions 152, each protrusion having a hole 154.Within each hole is a receiving member 156 which, due to its positionwithin the hole 154, cannot be seen in FIG. 1B and is more clearlyillustrated in FIGS. 5A and 5B which are described below. Thesereceiving members 156 are metal and also serve to provide groundingconnections between the camera and the external communication interface.There are also electrical contacts 158 which allow an electricalconnection between the camera 100 and an external communicationinterface. Because of the existence of the slots 160 for receivingvarious types of cards (e.g., memory or communication PCMCIA cards)there is very little depth for the connection portion 150. Thisrequirement resulted in the design of a novel connection mechanismdescribed in further detail below. Additionally, a conductive ribboncable which is thin and flexible is used to feed power and receive andtransmit signals through the contacts 158.

The camera also includes contacts 162 on the side of the camera andconnectors 164 which allow connection of a video display and a speakerto display images and audio generated by the camera.

FIGS. 2A-2C illustrate perspective views of an external communicationinterface 180. The interface 180 includes, as illustrated in FIG. 2A, asliding release button 182, a DIN 8 pin RS-422 interface for connectionto a modem port of a Macintosh computer and a 9 pin D connector 188which communicates according to the RS-232 format to an IBM compatiblepersonal computer. Images and/or audio are communicated between theconnected computer and camera in either direction. The interface 180also includes nuts 186 for receiving screws from a pin connector whichplugs into the D-9 pin connector 188. FIG. 2B is a perspective viewshowing the underside of the communication interface 180 which connectsto the camera 100. A clearer view of this connection portion 190 is seenin FIG. 2C.

The connection portion 190 includes convex indentations 194 which matchwith the concave protrusions 152 of the camera. The convex indentations194 include pivoting latches 196 which latch with the receiving member156. The communication interface also includes pins 192 which correspondto the contacts 158 of the camera.

FIG. 3A illustrates a latching mechanism 200 located within the externalcommunication interface 180 which is used to connect the externalcommunication interface 180 to the camera 100. The latching mechanism200 includes a frame 202. On the frame is mounted a spring connector 204which is used to mount a spring which is connected to a sliding releaseunit which is illustrated in FIG. 7. There is a pivoting latch member210 which includes the latch 196 and is resiliently held in place via aspring 206.

FIG. 3B is a cross-sectional view of the latching mechanism 200illustrated in FIG. 3A. In this figure, it is seen that the frame 202 isnot planar but has the center portion thereof raised above a level ofthe region supporting the pivoting latch member 210. This allows thelatching mechanism 200 to be mounted to a board, for example a printedcircuit board, having holes to accommodate the end regions of the frame.Only the center region of the frame is mounted on the printed circuitboard.

FIG. 4A is a top view of the pivoting latch member 210. The pivotinglatch member 210 contains a body 212 which is pivotally mounted at apivot point 214. Connected to the body 212 is the latch 196 and apressing surface 216. FIG. 4B is a cross-sectional view of the pivotinglatch member 210. This figure clearly shows that the latch 196 is at alevel below the level of the body 212. This allows the latch 196 to beinserted into the hole 154 of the camera. Further, the level of thepressing surface 216 is shown to be above the level of the body 212 ofthe pivoting latch member.

FIGS. 5A and 5B are a perspective view of the operation of connectingthe latch 196 of the external communication interface 180 to thereceiving member 156 of the connecting portion of the camera. In FIG.5A, first the latch 196 is pushed downwardly to the level of thereceiving member 156. Next, the latch 196 is pushed through thereceiving member 156 in order to engage with the receiving member 156 asillustrated in FIG. 5B. Referring to FIG. 5A, as the latch 196 is pushedforward through the receiving member 156, the surface 196A of the latch196 contacts the surface 156A of the receiving member 156. The roundedsurface 196A of the latch 196 causes the latch 196 to pivot and thenengage with the receiving member 156, as illustrated in FIG. 5B.

FIGS. 6A and 6B are a top view of the interaction of the pivoting latchmember 210 with the receiving member 156. In FIG. 6A, the pivoting latchmember 210 is engaged with the receiving member 156 and corresponds tothe perspective view illustrated in FIG. 5B. In order to release thelatch 196 from the receiving member 156, a force is applied against thepressing surface 216 which pivots the latch member 196 so that the latchmember 196 and the entire external communication interface can be slidback so that the latch 196 is no longer under the receiving member 156.Then, the latch 196 along with the entire external communicationinterface can be separated from the camera by moving the externalcommunication interface away from the camera.

FIG. 7 is an exploded view of the internal components of the externalcommunication interface 180. There is a sliding release unit 222 havingends which engage with the pressing surfaces 216 of the pivoting latchmember 210. The exact position of the sliding release button 182illustrated in FIG. 2A can be seen in FIG. 7. There is a groove 224 inthe sliding release unit 222 which mates with and receives the springconnector 204. The spring connector 204 slides along this groove 224.There is also a spring connector 226 on the latching mechanism 222. Aspring (not illustrated) connects to the spring connector 204 and thespring connector 226. This keeps the sliding release unit 222 biasedaway from the pressing surfaces 216. In order to operate the releasemechanism, the sliding release unit is pushed towards the pressingsurfaces 216 in the direction of the arrow on the sliding release button182 which causes the latches 196 to pivot inwardly or towards eachother.

The frame 202 of the latching mechanism spans the two holes 232 in aprinted circuit board 230. Due to the offset levels of the frame 202,the ends of the frame containing the pivoting latch members 210 fitwithin the holes 232. Mounted on the printed circuit board 230 is asignal level conversion chip 234 which is described in detail below.Connected to the signal level conversion chip 234 are the 8 pin RS-422connector 236 and the 9 pin D connector for RS-232 signals.

FIG. 8 is a block diagram showing the details of the construction of thecamera 100. The microphone 1 is connected to an amplifier/filter 2 a,which outputs a signal to an analog-to-digital converter 4. Theamplifier/filter 2 a reduces the audio signal to the appropriatebandwidth. The analog-to-digital converter 4 operates with an optimumsampling frequency, for instance, at a frequency which is aninteger-times of the sub-carrier frequency of an NTSC signal used by thecamera. Further, a sampling frequency of the A/D converter 4 is morethan two times the necessary bandwidth. An audio datacompression/expansion circuit 3 is used to encode and decode audiosignals using known methods of audio encoding such as linear PCM, DolbyAC-3, or MPEG-2 audio encoding. The compressed audio signals aretransmitted to a conventional FIFO circuit 13 which functions as amemory and alternatively can be a DRAM. The FIFO circuit 13 includes asection for images and a section for audio. Unencoded digital audiosignals from the compression/expansion circuit 3 are transmitted to adigital-to-analog converter 5 and subsequently amplified and filtered bythe amplifier/filter 2 b. The audio signals included in the signals 26are then output to a suitable audio generator such as a speaker 32.

An image photographing section 6 of the camera includes a photographinglens 7, a lens opening 8, an image photographing element 9 such as a CCD(charge coupled device) or a MOS-type image photographing element. TheCCD 9 in the preferred embodiment has a resolution of 768×480(horizontal×vertical). The output of the CCD 9 is transmitted to acircuit 10 which eliminates noise from the analog signal output by theCCD 9. This may be accomplished by a correlative doubled sampler (CDS).The out put image signal from the image photographing portion 6 istransferred to an analog-to-digital converter 4 which transmits adigital image signal to a digital signal processing circuit 11 which,for example, performs ordinary and known treatment of the image signalincluding gamma-compensation, color separation, and generates theluminance signal Y, and color difference signals Cb and Cr in a knownmanner. An example of the performance of these functions is disclosed inU.S. Pat. No. 5,343,243, which is incorporated herein by reference.Video signals (either analog or digital) are output from the digitalsignal processing circuit 11 as a video signal 26 which is displayed bya display such as a color LCD panel.

An image data compression/expansion circuit 12 is used to encode anddecode the images using known image compression methods which transformthe images into and out of compressed formats such as GIFF, JPEG, MPEGor any other known image compression method. Details of imagecompression which may be used by the camera 100 are disclosed in U.S.Pat. No. 5,414,464 which is incorporated herein by reference. A cardinterface circuit 14 is connected to the card connector 17 through thecard interface bus 25. The card interface circuit 14 controlscommunications between the camera and the plug-in communication cardswhich for example may function as a LAN card, a modem card either for aconventional wired telephone system or a cellular phone, a SmallComputer System Interface (SCSI) interface, a serial port, an ISDNinterface, or any other type of communication device. From interfacecircuit 14, images and audio are output to memory card 16 or I/O card15. The I/O card includes a cable 24 for connecting to an externaldevice. Also, images may also be transferred to interface circuit 14from cards 15 or 16.

A Central Processing Unit 23 (CPU) controls the operation of the cameraand is connected to a mode display 22 which displays various operatingparameters of the camera including modes which have been set andoperating parameters of the camera. The mode display 22 may be an LCD orLED display. An operating portion 21 through which the user inputscommands such as the command to take a picture when the shutter buttonis pressed, whether sound is recorded, whether still images or a seriesof still images forming moving images are recorded, and all otheroperations of the cameras. A flash 20 which is powered by batteries (notillustrated) is connected to the CPU 23 and is used to illuminate thescene to be photographed. There is a driver 18 which drives a mechanicalsystem of the image photographing portion 6 and performs functions suchas focusing and zooming of the lens. The timing signal generator 19generates various timing signals as images are captured such as avertical synchronizing signal, a horizontal synchronizing signal, and aCCD synchronizing signal.

Compressed images which are stored in the memory card 16 may be read outof the memory card 16 through the card interface circuit 14 and storedin the FIFO circuit 13. The compressed images are subsequentlytransferred to the image data compression/expansion circuit 12 whichdecodes or expands the compressed image signals and transfers thesignals to the digital signal processing circuit 11. In the digitalsignal processing circuit, the luminance and color difference signalsare transformed to a NTSC signal and output as a video signal.

Compressed audio information is similarly read out of the memory card 16and written into the FIFO circuit 13. The encoded audio signals aretransferred to the audio data compression/expansion circuit 3 where theyare converted to an uncompressed digital form, converted to an analogform by the digital-to-analog converter 5, and amplified and filtered bythe amplifier filter 2 b. The converted signal is output as the audiosignal.

The digital images captured by the camera are used to create exposurecontrolling evaluation information, automatic focus controllinginformation, and automatic white balance evaluation information by theCPU 23. Automatic control of the camera is performed using thisinformation. Additionally, this and all other evaluation data, controldata, status data, etc., can be output through or stored in the I/O card15 or stored in the memory card 16. This information may be used, forexample, when monitoring the camera in order to determine if an abnormalstate exists. Further, the quality of the image can be optimized bychanging the number of pixels used to represent an image.

The CPU 23 also performs a clock function for recording the date andtime of when the audio and video has been captured. Additionally, afield number may be added to the image data by the CPU 23. Each of theimage data, audio data, date, time, and field number may be outputthrough the card interface circuit 14 to either the memory card 16, I/Ocard 15, or an interface circuit 27 which is an alternative device tothe I/O card 15 for communicating.

The interface circuit 27 converts signals which are communicated to anappropriate standard. For example, the camera according to the presentinvention can communicate according to the RS-232 standard or the RS-422standard. The interface circuit 27 is the structure which changes thesignals to the appropriate format. During operation, the user of thecamera will select the desired communication format (e.g., RS-232 forIBM PC compatibles and RS-422 for Macintosh computers). Both the RS-232and RS-422 are well known standards and one of ordinary skill in the artwould know how to build the appropriate circuitry to generate signalsaccording to the appropriate standard. For example, see e.g., “ControlTechnology and Personal Computers, System Design and Implementation”, byHordeski, 1992, published by Van. Nostrand Reinhold, which discusses asingle I/O expansion board which can transmit information according toeither the RS-232 or RS-422 standards, depending on the user's desires,which is incorporated herein by reference.

Signals within the CPU will generally have a voltage range of 0 to +5volts whereas bipolar signals in the range of approximately −15 volts to+15 volts are used with the RS-232 standard. The signal level conversioncircuit 28 functions to convert the signal to the appropriate levels andis preferably contained within the signal level conversion chip 234 ofthe external communication interface 180. A more detailed description ofthe circuit is explained with respect to FIG. 17. There is acommunication device 29 such as a personal computer, modem, or anothercamera, for example, connected to the signal level conversion circuit28. This communication device 29 exchanges digital files containingvideo and/or audio information. The camera can both export and importaudiovisual information.

In FIG. 8, the FIFO circuit or memory 13 is illustrated as beingconnected to each of the audio data compression/expansion circuit 3, theimage data compression/expansion circuit 12, the card I/F circuit 14,and the CPU 23, as an alternative, the FIFO circuit or memory 13 may bedirectly connected between the card interface circuit 14 and the CPU 23.In this case, the audio data compression/expansion circuit 3 isconnected to the card interface circuit 14 instead of being directlyconnected to the FIFO circuit 13. Further, as an alternative to any useof a FIFO circuit 13, a DRAM, an SRAM, or any other desired memory canbe used.

Details of the CPU 23 are illustrated in FIG. 9. In FIG. 9, the CPU 23contains a microprocessor 50, RAM 52 for storing various information andserves as a working memory area as calculations and functions are beingperformed, and a control program storing area 51. The control programstoring area 51 includes a section 55 for storing basic routines such asBIOS (Basic Input Output System) routines, and other routines used bythe system. The basic routines 55 are stored in a non-volatile memorysuch as a flash memory, an EPROM, or other type of memory. There is asection of the control program storing area 51 which stores rewritableand optional routines which may be loaded in from the memory card 16 andthe I/O card 15. Section 54 may be constructed using the same flashmemory as stores the basic routines 55 or may be a separate memory. Inorder to reduce the size of the chip and reduce the cost of the chipwhich may be used as the CPU 23, it is desirable to use a flash memoryto store the basic routines 55 and the rewritable and optional routines54. The CPU 23 may either be a single chip or be composed of multiplecomponents. By having a section for rewritable and optional routines,the camera becomes very flexible by allowing the camera to be programmedas desired and there is no need to store routines which are not going tobe used. This rewritable and optional routines section is especiallyuseful for the process of inputting and outputting information as thereare many different communication protocols which may be used. Thecontrol program storing area 51 stores routines which control thefundamental functions of the camera and other functions such as readingout program data, changing parameters within the camera, writing datainto the rewritable and optional routines section 54, and any otherfunction of the camera. Supplemental circuitry 53 performs functionswhich are necessary for the CPU and includes a bus controller, a serialcommunication controller, an interrupt controller and analog-to-digitalconverter for monitoring analog signals, and a clock for keeping trackof the time and date.

FIG. 10 illustrates a possible structure for the memory card 16. In thisexample, the memory card includes four buffers 41A-41D which arerespectively connected to four flash memories 40A-40D. The buffers 41may be implemented using 256 byte SRAMs and the flash memoriesimplemented each using a 16 Mbit flash memory. The flash memories may beconventional and can be NAND type flash memories available from Toshiba.Alternatively, the memories can be a NOR type flash memory availablefrom Intel. The memory card 16 is connected to the card connector 17through an eight bit data bus.

The buffers 41 are relatively high speed buffers whereas the flashmemories 40 are relatively slow memories. The high speed buffers 41 mayoperate as burst transfer memories. During operation, information istransferred to the buffer memories and subsequently transferred to thecorresponding flash memory in groups of 256 bytes. Accordingly, aplurality of transfer operation will usually be needed to transfer thedesired material into or out of the memory card 16. The number oftransfers between the buffers 41 and the FIFO circuit 13, for example,is set to be an integral multiple of a transfer size of the memory card.It is also possible for the number of transfers to be the amount ofinformation to be transferred divided by the total size of the buffers41, rounded up to the nearest integer. As an alternative to flashmemories, the memories 40 can be implemented using EPPROMs.

FIG. 11 illustrates a process for capturing and storing video and audioinformation. After starting, the user presses the shutter release button124 and a single picture along with associated audio is captured andstored in step 252. Step 254 then compresses the image and audio.Separate image and audio files are then written into the memory card 16in step 256. Subsequently, a relation file which describes theassociation of the image and audio files is written or updated in step258. The process of FIG. 11 then ends.

An example of the organization of files is illustrated on the left sideof FIG. 12. The left side of this file illustrates memory card 16 havingthree video files 262A-262C, each having a header. The video files arestored in a compressed form such as according to the JPEG format. Thereare also two audio files 264A and 264B each containing headers andhaving been encoded using adaptive pulse coded modulation (PCM). Arelation file 266 describes the correspondence between the video andaudio files. For example, video file three 262C contains one image andcorresponds with the audio in audio file two 264B and the relation file266 describes this correspondence. The relation file 266 may alsofunction as a directory of information within the memory card 16. Therelation file can indicate information of just a still image, thecombination of a still image with audio data, and information of asuccessive images so that a series of images can be displayed togenerate moving images. Further, if desired, the relation file will alsostore directory information indicating the location of the necessaryfiles. The manner of storing information within the memory card 16 ispreferably implemented according to known standards. For example, theinformation is preferably stored in a PCMCIA compatible memory cardconforming to the PC Card Standard which conforms to the JEIDA SpecificExtensions. This standard is described in the publication entitled “PCCard Standard”, Vol. 12, JEIDA Specific Extensions, May, 1995 availablefrom JEIDA (Japan Electronic Industry Development Association), which isincorporated herein by reference.

A feature of the present invention is the omission of a separate switchwhich is used to place the camera in a communication mode. Conventionaldigital cameras have a specific switch which changes the camera from arecord or play mode to a mode which allows the transmission and receiptof images and audio. A description of how the invention operates withoutsuch a switch is set forth in detail below.

FIG. 13A illustrates a switch 110 which corresponds to switch 110illustrated on the camera 100 in FIG. 1A. The switch is a three positionswitch having an off, a play and transmit position, and a record andreceive position. When the camera detects that the communication mode isto be used, as explained below, the receive or transmit functions areselected. When the camera is not to communicate, the record or playfunctions are selected. As an alternative, FIG. 13B illustrates twoseparate switches 282 and 284, one for determining whether the camera isto be in a receive or transmit mode, and another for deciding whetherthe camera is to record images, play images, or to be turned off. InFIGS. 13A and 13B, the switches are slidable between the position theswitch is in as illustrated by a solid circle and the other possiblepositions for the switches illustrated by broken circles.

FIG. 14 illustrates a flowchart of the overall process of transmittinginformation by the camera, or receiving information by the camera froman external device. The external communication device can be a computer,another camera, or any other device which receives and/or transmitsinformation from the camera. After starting, the user connects thecamera to a communication device such as a computer in step 302. At thistime or prior to this time, the user will select the type ofcommunication protocol which is to be utilized such as for example, theRS-232 protocol or the RS-422 protocol. Step 304 detects whether thecamera is connected to the communication device. This can be performed,for example, by monitoring the Data Terminal Ready (DTR) signal when thecommunication protocol which is being used is RS-232. The signal linewhich is monitored is pin no. 4 of the nine pin D connector 188. Bymonitoring this electric signal from the communication device such asthe computer, the switch which places the camera in a communication modecan be eliminated, thus reducing the weight and complexity of thecamera. Step 304 has been described with respect to the DTR signal of anRS-232 protocol but any other signal of any other communication protocolwhich performs a similar function and indicates that the communicationdevice is ready to receive or transmit information from or to the cameramay be utilized. Step 304 is repeated until the appropriate signal isdetected, indicating that the communication device is ready tocommunicate with the camera. Step 304 is preferably performed every ½ to1 second, although longer or shorter times can be utilized.

After an affirmative response from step 304, step 306 is performed whichexecutes or sets up the appropriate communication algorithms within thecamera so that the camera will be prepared to transmit or receiveinformation. As an example, before this time, the communication linesexcept for the DTR line may not be monitored in order to avoid thedetection of improper or spurious signals which may occur before orduring connection. Step 308 then detects whether the camera is totransmit or receive information based on the position of switch 110illustrated in FIG. 13 or switch 282 illustrated in FIG. 13B. If thecamera is in a transmit mode, step 310 is performed which transmits dataaccording to the process illustrated in FIG. 15. If information is to bereceived by the camera, steps 312 and 314 respectively receive and storethe data according to the process illustrated in FIG. 16. The process ofFIG. 14 then ends.

FIG. 15 illustrates a process for transmitting information such as imageand audio information out of the camera. In order to transmit theinformation out of the camera, first the relation file from the memoryca rd is read in step 320. The relation file indicates thecorrespondence between the image and audio files. Additionally, therelation file will store directory information of the image and audiofiles. Based on the information in the relation file which has been readin step 320, the image file and the associated audio file are read instep 322 and transferred to the FIFO memory 13 in step 324. These twofiles are combined in step 326 and the resulting data does not containany relation information. The combined image and audio files areillustrated as 270 in FIG. 12.

In FIG. 12, the combined image and audio files include a header andcorresponding video file 262 and a header along with corresponding audiofile 264B. In the example illustrated in FIG. 12, video file onecorresponds to audio file one and video file three corresponds to audiofile two but there is no corresponding audio information for video filetwo. After the video and audio information has been combined, thecombined information is transmitted out of the camera in step 328 andthe process of FIG. 15 ends.

FIG. 16 illustrates the process for receiving information by the camera.In step 340, combined image and audio files are received for example,through the I/O card 15 or from the communication device 29 through thesignal level conversion circuit 28 and the interface circuit 27. Whenthe received information is from the I/O card, or alternatively from theinterface circuit 27, the received image and audio files are stored inthe FIFO memory 13 in step 342. Next, this combined image and audioinformation is separated in step 346. The audio information is writteninto the memory card and the image information is also written into thememory card in step 348. Next, the relation file of the memory card 16is updated to describe the relationship between the newly received audioand image files in step 350 and the process of FIG. 16 then ends. Therelationship information of the memory card indicates that the audio andimage files correspond to each other and are to be presented or playedat the same time. The relationship information is determined based onthe transmission as a unit of the image and audio files.

Another feature of the present invention is the manner in which thedigital signals representing images and audio generated within thecamera are converted to signals conforming to the RS-232 standard.Unlike the logic signals normally used with a microprocessor within thecamera, RS-232 signals are bipolar. This means that a level of zerovolts (which corresponds to ground) does not indicate a logical lowlevel but a negative voltage level is necessary to represent a logicallow level. The voltage value for a “1” is preferably between +5 volts,and +15 volts and for a “zero” preferably between −5 volts and −15volts.

In order to convert signals to their appropriate levels, there is asignal level conversion chip 234, illustrated in FIG. 17, within theexternal communication interface 180. This signal level conversion chipis, for example, a commercially available integrated circuit such as theMAX 213 CAI available from Maxim, or the UP04724 available from NEC. Thesignal level chip 234 is connected between the interface 27 and theconnectors 238 and 236 according to known manufacturer's specifications.The nine pin D connector 238 and eight pin DIN connector respectivelyhave the pin definitions as set forth in Table I and II below. TABLE I 9PIN D RS-232 CONNECTOR Signal Signal Function Number AbbreviationFunction 1 CD Carrier Detect 2 RD Received Data 3 SD Send Data 4 ER DataTerminal Ready 5 SG Signal Ground 6 DR Data Set Ready 7 RS Request toSend 8 CS Clear to Send 9 CI Call Indicate

TABLE II 8 PIN DIN RS-422 CONNECTOR Signal Signal Function NumberAbbreviation Function 1 HSKO Handshake Output 2 HSKI Handshake Input 3TXD- Transmission Data 4 GND Ground 5 RXD- Receiving Data 7 GPI CallIndicate

The power supplied to the signal level conversion chip. 234 originatesfrom the camera. The signal level conversion chip 234 may consume power,even when no communication operation is occurring. In order to extendthe battery life of the camera by not wasting power unnecessarilypowering the signal level conversion chip 234, the present inventionemploys a power conservation feature which places the signal levelconversion chip 234 in a low-power mode or standby mode. As an exampleof the operation of the power conservation function, there is a timingdiagram illustrated in FIG. 18. The top line of this diagram illustratedthe occurrence of communication and the bottom line illustrates when thecommunication circuitry such as the signal level conversion chip 234 ispowered. In this figure, it can be seen that the communication circuitryis powered for a short time before and after the occurrence ofcommunication. When communication is not occurring, the power to thecommunication circuitry is turned off or changed to a standby mode.

In order to place the communication circuitry or signal level conversionchip 234 in the standby or low-power mode, the CPU within the cameramonitors the Data Terminal Ready (DTR) line of the RS-232 connection.When this line is low, the external communication device such as acomputer is not ready to perform communication and the signal levelconversion chip may have the power thereto reduced. To the contrary,when the DTR signal is high, the external device is ready to communicatethrough the signal level conversion chip and accordingly, thecommunication circuitry must be powered. The checking of the signalwhich indicates that communication is ready to occur is performed atleast once every second in the preferred embodiment. However, thischecking frequency may be made shorter by checking the DTR signal onceever at least one half second or longer by checking the DTR signal onceevery five seconds, once every ten seconds, or even longer.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. For example, theinvention can be implemented using one or more microprocessors,integrated circuits, convention circuit elements or other desiredhardware. It is therefore to be understood that within the scope of theappended claims, the invention may be practiced otherwise than asspecifically described herein.

1. A method of detecting communication between an electronic camera andan external device, comprising the steps of: detecting, by theelectronic camera, that the electronic camera is connected to theexternal device and the external device is in a state which permitscommunicating; and communicating between the electronic camera and theexternal device, when the electronic camera is detected to be connectedto the external device and the external device is detected to be in astate which permits communicating.